JPH1184852A - Sensitivity adjusting method of toner concentration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automate adjustment by smoothening a pulse train in which high and low levels are repeated, with a low-area-pass filter and making a sensitivity adjusting voltage inputted to a toner concentration sensor variable. SOLUTION: The sensitivity adjusting voltage outputted from the low-area- pass filter 5 is converted into a digital signal by an A/D conversion circuit 7, to be fetched in a CPU 6, so that the feedback control of the sensitivity adjusting voltage is executed to make a voltage for showing the output value of the A/D conversion circuit 7 coincident with a voltage recorded in a nonvolatile memory, at the time of initializing the sensitivity adjusting voltage. The cycle of the pulse train inputted to the low-area-pass filter 5 is defined as T and the ratio of a H-level time per cycle of the pulse train 10 is defined as (x) and when x=0 is obtained, the pulse train is always at the L-level, so that the sensitivity adjusting voltage becomes 0V. Further, when x=1 is obtained, the pulse train adjusting voltage is always at the H-level, so that the sensitivity adjusting voltage becomes 0V. Further, when 0<x<1 is obtained, the voltage level of the pulse train is timewisely averaged by the low-area-pass filter 5 and the sensitivity adjusting voltage is proportioned to the ratio (x).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the sensitivity of a toner concentration sensor, and more particularly to a method for adjusting the sensitivity of a magnetic sensor for detecting the toner concentration of a two-component developer comprising a toner and a magnetic powder carrier.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional method for adjusting the sensitivity of a toner density sensor. As shown in FIG. 4, in the prior art, a voltage obtained by dividing the power supply voltage of the toner density sensor 1 by a resistor R and a variable resistor VR is input as a sensitivity adjustment voltage, and the toner density sensor in a developer having a reference density is input. The value of the variable resistor VR has been adjusted so that the output voltage of No. 1 becomes a predetermined level.

[0003]

In the above-described sensitivity adjusting method of the toner density sensor according to the prior art, the variable resistor VR must be adjusted to set the sensitivity adjusting voltage. It is necessary to mount the variable resistor or the board with the variable resistor at a position where the variable resistor can be adjusted, and the mounting positions of the developing machine, the toner density sensor, and the variable resistor (or the board with the variable resistor) are limited. I was

[0004] Further, due to the detection accuracy of the toner concentration and the mounting space, when the variable resistor or the substrate must be mounted at a position where the variable resistance cannot be adjusted while the developing machine is driven, the toner is required. In order to adjust the sensitivity of the density sensor, it was necessary to provide a dedicated adjustment facility.

Further, the mechanical work of adjusting the variable resistance hinders the automation of the adjustment work and causes a large adjustment error.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to change a sensitivity adjustment voltage input to a toner density sensor regardless of a mounting position of a developing machine or a toner density sensor. It is another object of the present invention to provide a method of adjusting the sensitivity of a toner density sensor, which enables the adjustment operation to be automated, and enables highly accurate sensitivity adjustment.

[0007]

An object of the present invention is to provide a two-component developing apparatus comprising a toner and a magnetic powder carrier, wherein an output voltage level at a reference magnetic permeability can be adjusted based on a sensitivity adjusting voltage inputted from the outside. In the method of adjusting the sensitivity of the toner density sensor that outputs a voltage corresponding to the magnetic permeability of the agent, a pulse train that repeats a high level and a low level at a constant period is smoothed by a low-pass filter, and the DC voltage generated thereby is reduced. This is achieved by using the sensitivity adjustment voltage.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a circuit for realizing a method for adjusting the sensitivity of a toner density sensor according to the present invention. In FIG. 1, a control board 4 includes a CPU 6,
A / D conversion circuits 7 and 8, a PWM timer 2, a voltage level conversion circuit 3, and a low-pass filter 5 are mounted.
The control board 4 includes at least a circuit for detecting the toner concentration, and may be, for example, a board for controlling the printing process of the electrophotographic apparatus, a board for controlling the entire electrophotographic apparatus, or a control board for the adjustment equipment. It may be.

The CPU 6 controls the toner density by converting the output voltage of the toner density sensor 1 mounted on the developing machine 9 into a digital signal by an A / D conversion circuit 8 and taking in toner density information. That is, the CPU 6 determines whether toner replenishment is necessary based on the acquired toner density information, and replenishes toner from the toner replenishing means (not shown) to the developing device 9 as necessary. However, the function of the CPU 6 is not limited to the toner density control, and may have a function related to another electrophotographic process.

Next, a method of generating the sensitivity adjustment voltage will be described. First, the PWM timer 2 outputs a pulse train that repeats the H (High) level and the L (Low) level at a cycle and a time ratio set by the CPU 6, and is input to the voltage level conversion circuit 3. The role of the voltage level conversion circuit 3 is to convert the voltage level of the output pulse train of the PWM timer 2, for example, converting the L level of the pulse train to +12 volts and the H level to 0 volts. The pulse train converted to 0 volts or +12 volts by the voltage level conversion circuit 3 is smoothed by the low-pass filter 5, and becomes a DC voltage corresponding to the time ratio between the H level and the L level of the output pulse train of the PWM timer 2, The sensitivity adjustment voltage is input to the toner density sensor 1.

In this embodiment, the sensitivity adjustment voltage output from the low-pass filter 5 is converted into an A / D signal in consideration of variations in the components constituting the PWM timer 2, the voltage level conversion circuit 3, and the low-pass filter 5. The signal is converted into a digital signal by the conversion circuit 7 and taken into the CPU 6, and the voltage represented by the output value of the A / D conversion circuit 7 matches the voltage recorded in the nonvolatile memory at the time of initial setting of the sensitivity adjustment voltage described later. The feedback control of the sensitivity adjustment voltage is performed.

In this embodiment, the voltage level of the pulse train output from the PWM timer 2 is
However, this conversion is not always necessary. If the variable range of the sensitivity adjustment voltage of the toner density sensor 1 is sufficient, the output pulse train of the PWM timer 2 is directly input to the low-pass filter 5. May be.

The method of generating the pulse train is not limited to the PWM timer 2. For example, the ON / OFF of the I / O port may be controlled by software, or the data of the flip-flop may be periodically transmitted. It may be a method of rewriting.

Further, when the influence of the error of the sensitivity adjustment voltage due to the variation of the components constituting the PWM timer 2, the voltage level conversion circuit 3 and the low-pass filter 5 on the output voltage of the toner density sensor 1 can be neglected, for example, When the sensitivity adjustment voltage described later is initially set, the ratio of the H level time to the L level time of the pulse train is recorded in the non-volatile memory, and the H level time recorded in the non-volatile memory when the toner density sensor 1 is operated. If a pulse train is generated at a ratio of L-level time, the sensitivity adjustment voltage can be controlled by an open loop in which the path from the low-pass filter 5 to the CPU 6 through the A / D conversion circuit 7 is omitted. is there.

Next, an example of an initial setting method of the sensitivity adjustment voltage will be described. A developer having a reference density is supplied to the developing device 9 and brought into an idling state (the electrostatic latent image does not exist on the photoconductor, that is, the developing device is not driven but the developing device is driven).
After a lapse of a sufficient time until the charged state of the developer is stabilized, the setting of the PWM timer 2, that is, the time ratio between the H level and the L level of the pulse train is gradually changed, and the output of the toner density sensor 1 becomes a predetermined value. (For example, 2 volts), the sensitivity adjustment voltage at this time is recorded in a non-volatile memory (not shown), and the initialization is completed.

Thereafter, the control board 4 adjusts the set value of the PWM timer 2 so that the sensitivity adjustment voltage becomes a value recorded in the nonvolatile memory at the time of power-on or initialization at the time of error reset. Further, the mounting position of the nonvolatile memory is not limited to the control board 4, and may be, for example, a control board for controlling the entire apparatus or the developing machine itself.

Next, the relationship between the ratio of the H level time of the pulse train 10 input to the low-pass filter 5 and the sensitivity adjustment voltage will be described with reference to FIG. The period of the pulse train 10 is represented by T, and the ratio of the H level time per one period of the pulse train 10 is represented by x. When x = 0, since the pulse train 10 is always at the L level (0 volt), the sensitivity adjustment voltage becomes 0 volt. When x = 1, the pulse train 10 is always at the H level, so the sensitivity adjustment voltage is the H-level voltage of the pulse train 10. Further, when 0 <x <1, the pulse train 10
Is time-averaged by the low-pass filter 5, the sensitivity adjustment voltage is proportional to x.

Next, a configuration example of the voltage level conversion circuit 3 will be described with reference to FIG. FIG. 3A shows a configuration example of the voltage level conversion circuit 3 using an inverter (7406) having an open collector output. According to this configuration example, the PWM timer 2
Is high, the output of inverter (7406) is low.
Level, the output of the voltage level conversion circuit 3 becomes 0 volt, and when the output of the PWM timer 2 is L level, the inverter
Since the output of (7406) is open, the output of the voltage level conversion circuit 3 becomes +12 volts.

FIG. 3B shows a configuration example of the voltage level conversion circuit 3 using the transistor Tr. According to this configuration example,
When the output of the PWM timer 2 is at the H level, the transistor Tr
Is turned on, the output of the voltage level conversion circuit 3 becomes 0 volts. When the output of the PWM timer 2 is at the L level, the transistor Tr is turned off, so that the output of the voltage level conversion circuit 3 becomes +12 volts.

Therefore, in both cases of FIGS. 3A and 3B, the voltage level of the output pulse train of the PWM timer 2 is converted from 0 to +5 volts to +12 to 0 volts.

[0021]

As described above, according to the present invention,
The sensitivity adjustment voltage to be input to the toner density sensor can be changed regardless of the mounting position of the developing device and the toner density sensor, and furthermore, the adjustment work can be automated and the toner density sensor can be adjusted with high precision. A sensitivity adjustment method can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a ratio of an H level time of a pulse train input to a low-pass filter and a sensitivity adjustment voltage.

FIG. 3 is a block diagram illustrating a configuration example of a voltage level conversion circuit.

FIG. 4 is a block diagram showing an example of a conventional method for adjusting the sensitivity of a toner density sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Toner density sensor, 2 ... PWM timer, 3 ... Voltage level conversion circuit, 4 ... Control board, 5 ... Low-pass filter,
6 CPU, 7, 8 A / D conversion circuit, 9 developer, 1
0: pulse train.

Claims (2)

[Claims] An output voltage level at a reference magnetic permeability can be adjusted based on a sensitivity adjustment voltage input from the outside, and a voltage corresponding to the magnetic permeability of a two-component developer composed of a toner and a magnetic powder carrier. In the method for adjusting the sensitivity of a toner density sensor that outputs a signal, a pulse train that repeats a high level and a low level at a constant period is smoothed by a low-pass filter, and a DC voltage generated thereby is used as the sensitivity adjustment voltage. A characteristic method of adjusting the sensitivity of the toner density sensor. 2. The method according to claim 1, wherein the ratio between the high level time and the low level time of the pulse train can be set arbitrarily.